This invention relates to a computer graphic drawing apparatus, and more particularly to an improved computer graphic drawing apparatus having a fine adjusting device operatively disposed therein for making fine adjustments through an associated host computer during graphic drawing operations
Computer graphics has become one of the major functions of a computer. Graphs, charts, drawings, etc., are usually created with a graphic drawing apparatus or "electric mouse" which is electrically connected to an associated host computer through a transmission interface. The structure of the conventional computer graphic drawing apparatus or electric mouses is shown in FIG. 1 wherein when the housing unit A1 of the electric mouse is operated to move, a steel ball A2 will be moved along with the housing unit A1. If the steel ball A2 moves forward and backward, as the arrows indicate, an Y-axis revolving member A4 rotatably engaged with the steel ball A2 and a Y-axis disk A5 rotatably connected with the revolving member A4, will be moved along with the movement of the steel ball A2. As the Y-axis disk A5 continues to rotate, a plurality of light travel apertures A6 evenly formed in the Y-axis disk A5 will constantly be turned to align with a pair of light passing holes A8 provided in a light shielding plate A7. This plate is disposed in the housing unit A1 over the Y-axis disk A5 so that the red light transmitted from a light transmitter A9 will be intermittently passed through the light passing holes A8, when aligned with the light travel apertures A6, and received by a light receiver A10 from which signals will be fed into the IC. The IC is electrically coupled with an associated host computer (not shown), and the `cursor` on the CRT of the host computer will be moved in vertical direction. In like manner, when the housing unit A1 is moved horizontally, an X-axis revolving member A11, together with an X-axis disk A12, will be rotated with the `cursor` of the host computer, effecting a horizontal movement on the CRT. As can be seen from the above description and illustration, the known computer graphic drawing apparatus or electric mouse can only draw long lines and make coarse adjustments during the drawing operations through the movement of steel ball A2. In order to reduce the number of inevitable adjustments during graphic drawing operations, the housing unit A1 must be carefully operated. However, since the steel ball A2 can hardly be kept stable during coarse line drawing operation, it usually takes a great deal of time to accomplish a graphic drawing operation on the CRT terminal.